Chapter 11, Problem 11.24P

A counterflow, concentric tube heat exchanger used for engine cooling has been in service for an extended period of lime. The heat transfer surface area of the exchanger is ${\text{5 m}}^2$ and the design value of the overall convection coefficient is $38{\text{ W/m}}^2\cdot \text{K}$ . During a testrun, engine oil flowing at 0.1 kg/s is cooled from110°C to 66°C by water supplied al a temperature of25°C and a flow rate of 0.2 kg/s. Determine whetherfouling has occurred during the service period. 1f so, calculate the fouling factor, $R_f^n\left({\text{m}}^2\cdot \text{K/W}\right)$ .